Progress in understanding the function of human brown adipose tissues [HBAT] and hopefully eventually being able to use this improved understanding to help control the current obesity epidemic will require the development of "tools and methods capable of measuring the mass of BAT in human populations and to measure metabolic activity of HBAT". The aim of the proposed research program is to meet these needs by developing user-friendly, non-invasive, and completely safe microwave radiometers specifically designed for HBAT research. The radiometers will be based on handheld, self-calibrating, digital radiometers developed previously by MMTC, Inc. under sponsorship of NIH. They will be designed to be capable of operating in either passive or active modes that can respectively measure the metabolic activity and mass of HBAT and meet all applicable FDA safety standards for medical devices. Application will be made to the FDA to obtain approval for these radiometers. Radiometer antennas with fixed and variable depth of penetration into tissues will be fabricated and tested in tissue equivalent phantoms. The measured radiometric temperatures and locations of heated deep-seated simulated HBAT will be cataloged for a variety of phantom configurations and various antennas and all data will be assembled in a form that aids in the interpretation of passive and active microwave radiometric measurements of HBAT. After successful completion of the testing of the radiometers in phantoms, the dual- mode radiometers will be tested on 10 healthy young volunteers on whom FDG PET/CT scans will be performed to verify uptake of the radioactive tracers in activated and non- activated HBAT states induced by hot/cold environments. The tests will be performed at Johns Hopkins University School of Medicine and supervised by Richard L. Wahl, M.D., F.A.C.R., Professor of Radiology and Oncology and Henry N. Wagner, Jr. Professor of Nuclear Medicine who has done pioneering work on HBAT using PET/CT scans. The ultimate goal of this work is to replace the radiation and cost of PET/CT with a safe, faster, and cheaper microwave radiometry method. Only by directly comparing the relative gold standard of FDG in the stimulated and non-stimulated HBAT states in humans with the new method can we determine the radiometry operating characteristics in man. PUBLIC HEALTH RELEVANCE: The proposed program is for the development of a medical device designed to aid healthcare professionals in gaining a better understanding of the role of human brown fat in fighting obesity. This better understanding can be expected to lead to improved methods for treating obesity, the current epidemic of obesity being responsible for many sicknesses and early deaths.